1. Field of the Invention
The present invention relates to metal palmitate-dimethyl sulfoxide complexes and their method of preparation. The invention also concerns the use of metal palmitates, alone or complexed with dimethyl sulfoxide, as an antiwear additive in lubricating oils.
2. Description of Related Art
Metal complexes prepared from dialkyl sulfoxides have been known for a number of years (see "Complexes of Sulfoxides. I. Octahedral Complexes of Manganese (II), Iron (II), Cobalt (II), Nickel (II), and Zinc (II)," Currier, W. F. and Weber, J. H. Inoro. Chem. 6, 1539 (1967); and "Preparation of Several Sulfoxide Complexes with Group IV Organometallic Compounds," Langer, H.G. and Blut, A. H., J. Oroanometal. Chem. 5(3), 288-91 (1966)). For example, U.S. Pat. No. 4,104,310 discloses the preparation of a catalytically active complex from dimethyl sulfoxide and metal salts in which the possible organic anions include acetate, tartrate, benzoate or oxalate groups. As another example, U.S. Pat. No. 4,618,722 discloses the preparation of lubricant additives from a metal carboxylate and a hydrocarbyl halide in the presence of dimethyl sulfoxide (as the reaction solvent) to yield dihydrocarbyl sulfides.
However, none of the foregoing references disclose metal palmitate-dimethyl sulfoxide complexes, their method of preparation and use as antiwear additives in engine lubricating oils.